Heavy duty shackle

ABSTRACT

A heavy duty shackle for use under great loads, such as in anchor lines. The shackle is formed from a cylindrical bar rod by shaping the ends to a reduced diameter, and forging the central portion into a flattened shape having the cross-section of a wide shallow U shape. The bottom surface of the central section is in the form of a portion of a circular cylinder. The ends of the bar are flattened and a central opening is forged and based for a pin. The formed bar is then bent in the form of a bow to provide an eye for the shackle, with two parallel ears spaced a selected distance apart.

BACKGROUND OF THE INVENTION

This invention lies in the field of heavy duty cable fittings. Moreparticularly, it concerns the design of a very heavy duty shackle, suchas would be used in an anchoring system, and subjected to forces ofseveral hundred tons or more.

In the prior art, shackles in the form of a U shape, with pins whichpass through openings in the ears, have been constructed of round barstock, which is flattened on the ends, drilled for a pin, and then bentinto a U shape. Such shackle bows having a round cross-section areunsatisfactory, since they provide a very small radius around which aheavy wire rope must bend when in use. With small size wire ropes, athimble is often used, which will provide a surface of greater radius,to support the wire rope and utilize the full strength in the wire rope.However, for very heavy loads a thimble is not practical, and there isconsequently a weakness in the use of a heavy wire rope when bent arounda small radius shackle.

SUMMARY OF THE INVENTION

It is a primary object of this invention to provide a heavy duty shacklebow which has a cross-section, the inner surface of which is in theshape of a part of a cylinder, which has a radius greater than theradius of the round bar from which it is fabricated.

It is a further object of this invention to provide a cross-section forthe bow of a heavy duty shackle, which provides a greater length ofcontact between the bow and the wire rope looped through the eye of theshackle.

It is a further object of this invention to provide a cross-section ofthe shackle bow that has a greater section modulus than the originalcircular cross-section, and has a lighter weight and provides a greaterstrength than a bow of circular cross-section.

These and other objects are realized, and the limitations of the priorart are overcome in this invention, by manufacturing a heavy dutyshackle bow from a round rod of selected length and diameter D, by firstfullering the two ends to a selected smaller diameter D'. There are twoshort transition conical sections between the central portion ofdiameter D and the two end portions of diameter D'. The central portionis forged into a somewhat flattened shape which has a cylindricalsurface on the bottom, and a shallow U shape on the top. The shape ismuch wider then the diameter D and has a greater section modulus thanthe original cylindrical shape.

The shape is substantially of constant thickness of cross-section, sothat in heat treatment the properties of the metal will be much moreuniform than where the thickness of the metal varies throughout thecross-section. The contact length between the inner surface of theshackle bow and a wire rope connected thereto, is greater than thelength of contact of the inner surface of a shackle bow made out ofround stock.

The radius to which the wire rope is bent around the inner surface ofthe shackle bow is much greater than the radius of the original bar andis at least twice that of the original bar.

The two fullered ends of the rod are flattened and broadened, and holesare forged and drilled for the pin that locks the shackle.

The forged bar is then bent in the form of a bow with a more or lesscircular eye, and having two ears which are spaced apart a selecteddistance for entry of the wire rope loop.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and advantages of this invention and a betterunderstanding of the principles and details of the invention will beevident from the following description taken in conjunction with theappended drawings in which:

FIGS. 1A and 1B represent views of the original bar rod and the barafter fullering, respectively.

FIGS. 2 and 3 illustrate plan and elevational views of the forged rod.

FIG. 4 illustrates the various cross-sections of the forged rod atselected points along its length.

FIGS. 5, 5A and 6 show two views of the completed shackle, and a detailof the pin.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings there is shown in FIG. 1A a view of acylindrical rod of selected half length 13 and diameter 14 or Xindicated generally by the numeral 12.

FIG. 1B shows the shape of the rod after fullering, in which thediameter of the ends has been reduced from the original diameter 14 to alesser diameter 16 or X'. The central portion 24 of the rod now extendsfrom the mid-point a distance 23 at the original diameter 14. There isthen a short portion 27 of more or less conical transitional shape, fora length 21, to a plane 22, and then a portion 26 of length 25 ofconstant diameter 16.

The fullered rod 26 of FIG. 1B is then forged into the shape shown inFIGS. 2 and 3, and in the various cross-sections shown in FIG. 4. Thecentral portion 24' as at plane 18 is flattened and broadened into asection shown in A of FIG. 4. This has on the underside a cylindricalsurface 31, and on the top a flat surface 30 with a depressed centralportion 28, which provides a shallow U-shaped cross-section. The radiusof the cylindrical portion 31 is at least twice the radius of theoriginal rod 12.

The depression 28 becomes shallower and narrower in the region of therod between the planes 20 and 22, where the cross-section at plane B isshown as B in FIG. 4. Here the width of the cross-section and its radiusare reduced from that of A and the shape merges into a somewhatflattened cylinder shown by C in FIG. 4, and indicated for the portion Cof FIG. 3.

The end of the portion 26 of FIG. 1B is flattened and broadened in orderto form a portion where there is a central opening for a pin, withsufficient material surrounding the depressions 34 to provide sufficientstrength to carry the load of the shackle. In the center of thisbroadened portion there are depressions 34 on top and bottom surfaces60, 61 which spread the metal outwardly to provide a thick rim 35. Thedepressions 34 are of somewhat lesser diameter than the diameter 38 ofthe opening that will be bored for the pin, shown in dashed lines 39.

In addition, the faces 60 and 61 of the ends that have been flattened toa thickness 64, have additional depressions 32 and 36 in each of thesurfaces. The purpose is to thin the cross-section and to provide betterheat treatment of the end portions of the shackle. These depressions 32and 36, which are somewhat arcuate in shape, have an additionaladvantage as will be explained, in connection with FIGS. 5 and 6, thatwhen the pin is inserted through the openings 39, that are bored in theends of the ears, there may be spurs or projections on the inner surfaceof the head of the pin, which lock into the depressions 32 and/or 36 andlock the pin against rotation.

The next step in the manufacture of the shackle is, of course, to formthe forged bar into a loop, which provides, as in FIGS. 5 and 6 anarcuate portion surrounding an eye 50, and rein sections 51 of more orless cylindrical cross-section, leading to the broader and thinner ears55 of the shackle which are spaced apart by distance 52 less than thediameter of eye 50. When completely bent into shape, the two openings 39are opposite each other, and a pin 54 can be inserted into the openings39 in the ears and locked by any selected means, such as, for example,by a threaded nut 58 and/or cotter pin as shown.

In the enlarged section FIG. 5A there is shown a detail of spurs orprojections 59 on the head 57 of the pin 54, which lock into the grooves32 and/or 36.

After the customary shackle is formed, it is then heat treated, as iscustomary. The change in cross-section is advantageous in providing amore uniform heat treatment, and development of the full strength of themetal E.

What has been described is a method of manufacture and a very heavy dutyshackle, which is forged with a specific type of cross-section, from around bar, which better utilizes the strength of the material, has agreater section modulus, reduces the overall weight of the shackle,increases the line of bearing contact between the wire rope and theshackle, and increases the radius of the contact surface, for betterutilization of the intrinsic strength of the wire rope.

By creating a specialized shape with the inner radius the equivalent tothe diameter of the basic stock size of the shackle, the contact lengthof the rope bearing surface has been increased by 58%. This increase inbearing or contact length naturally reduces the relative amount of wearon the wire rope or shackle bow by a corresponding amount.

By doubling the radius of the contacting surface this, in effect, meansthat the contacting wire rope is not bent around as small a radius andit increases the usable rope strength by a factor of 15%.

By utilizing the special shape section, the section modulus is increasedby 36% over what the normally-used round bar section would be.

By using a relatively contant cross-sectional thickness and keeping thisdimension the same as the normally-used round bar diameter, bettermetallurgical properties are achieved in the quenched and temperedmaterial to the extent of 6%.

The overall gain by the utilization of the shape section is an increasedstrength in the bow section of 42% over the conventionally-used roundbar diameter section.

Utilizing the special-shaped section and taking advantage of thebeforementioned strength increase in the section, achieves a 30-40%weight reduction over the same capacity shackle utilizing a round barsection of the same nominal configuration dimensions.

While the invention has been described with a certain degree ofparticularity, it is manifest that many changes may be made in thedetails of construction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure. It is understoodthat the invention is not limited to the embodiments set forth hereinfor purposes of exemplification, but is to be limited only by the scopeof the attached claim or claims, including the full range of equivalencyto which each element thereof is entitled.

I claim:
 1. The method of constructing a heavy duty shackle, for useunder large loads, such as with anchors, from a selected length of roundbar stock of diameter X, comprising the steps of:a. fullering, orreducing the diameter of the end portions of said bar, to a selectedlength, to a diameter X'; b. forging the center portion of diameter Xinto a broad flat U section, with the bottom surface of the U a portionof a circular cylinder;wherein the radius of said circular cylinder isat least substantially equal to diameter X' and the transversecross-section approaches approximately constant thickness; c. forgingthe ends into a section broader than, and thinner than X'; d. forgingdepressions in the two surfaces of said thinner ends, said depressionsapproximately arcuate, around a central hub; e. forging centraldepressions on each surface of said end hubs, of diameter smaller thanthe diameter of the pin to be used in the shackle; f. bending saidcentral portion into an arc, forming an eye, with the arms of a said Usection facing outwardly, and providing two parallel ears, the spacingbetween said ears less than the diameter of said eye, and greater thanthe dimension of an object to be looped over said shackle; g. drillingopenings through said ends concentric with said central depressions; andh. heat treating said shackle.
 2. The method as in claim 1 including theadditional steps of:a. providing a pin of diameter less than saidopening; b. forming a head at one end of said pin; c. forming at leastone spur on said head adapted to fit into one of said arcuatedepressions; and d. providing means on the second end of said pin tolock it in the openings in said ears.
 3. A shackle bow for heavy dutyuse .Iadd.with wire rope slings .Iaddend.under large loads, as in anchorlines, comprising:a. .[.a.]. .Iadd.an approximately circularcross-section .Iaddend.rein section adjacent the two ends of saidshackle for a selected length and of diameter X', each said rein sectionbeing between a central cylindrical portion and a flattened ear portion;b. said central cylindrical portion being of a broadened flattenedshape, having a U-shaped cross-section with a circular bottom surface,the radius of said bottom surface being at least substantially equal toX'; c. said shackle being in the shape of a bow, with said U-shape ofsaid central cylindrical portion directed outwardly, around a centraleye .Iadd.a distance of at least equal to one-half the circumference ofsaid central eye to where said central cylindrical portion joins witheach said rein section.Iaddend., said ears being substantially parallel,spaced apart a distance less than the diameter of said eye, and havingcoaxial central openings therein to receive a pin therethrough.
 4. Theshackle bow as in claim 3 including at least one substantially arcuatedepression, substantially concentric with said central opening on theouter surfaces of said ears.
 5. A shackle bow having an approximatelycircular eye, with two rein sections leading to two substantiallyparallel ears;the cross-section of said bow being in the form of a broadflat U section, within the bottom (inner) surface having as large aradius as possible; the thickness of the cross-section of said bowsubstantially constant; the cross-section of said rein sectionapproximately circular; the cross-section of said ears being broad andthin, with aligned central openings, and thick flanges formed by forgingcentral depressions in said ears; said shackle bow being heat treated.6. The shackle bow as in claim 5 including at least one substantiallyarcuate depression substantially concentric with said central opening onthe outer surfaces of said ears.
 7. The shackle bow of claim 5 includinga locked pin through said central openings.